JP5000027B1 - Nonvolatile memory device - Google Patents

Abstract

An oxygen-deficient transition metal oxide formed in a region covering the bottom and side surfaces of the first electrode wiring (151), the third interlayer insulating layer (16), and the memory cell hole (29) formed in a strip shape. A first resistance change layer (18a) configured, and a second resistance change layer (18b) configured of an oxygen-nitrogen-deficient transition metal oxynitride having an oxygen content different from that of the first resistance change layer (18a). The first electrode wiring (in the region covering the opening of the memory cell hole (29) and the first electrode (19) formed in the memory cell hole (29) and at least the opening of the memory cell hole (29). 151) and a first wiring (22) formed in a strip shape in a direction intersecting with 151), wherein the transition metal is M, the composition of the first resistance change layer (18a) is MO _z , and the second resistance change layer ( the composition of 18b) when expressed as _MO x _{N y,} > Meets the (x + y) the relationship.
[Selection] Figure 1

Description

  The present invention relates to a nonvolatile memory device using a resistance variable element. More specifically, the present invention relates to a nonvolatile memory device in which a plurality of resistance change layers having different oxygen contents are formed in a memory cell hole in order to realize element miniaturization and oxygen diffusion is prevented between the plurality of resistance change layers.

  2. Description of the Related Art In recent years, with the advancement of digital technology in electronic devices, development of large-capacity and non-volatile storage devices has been actively conducted in order to store data such as music, images, and information. For example, a nonvolatile memory device using a ferroelectric as a capacitor element has already been used in many fields. Further, in contrast to a nonvolatile memory device using such a ferroelectric capacitor, a resistance value is changed by application of an electric pulse, and a nonvolatile memory device (hereinafter referred to as Resistive RAM) using a material that keeps the state is maintained. Or ReRAM) has attracted attention because it is easy to achieve consistency with a normal semiconductor process.

  Patent Document 1 proposes a cross-point type ReRAM in which a resistance change layer is formed in each of minute holes arranged in a matrix in order to reduce the size of a memory element and increase the capacity of a memory device.

  By the way, chemical vapor deposition (CVD: Chemical Vapor Deposition), atomic layer thin film deposition (ALD: Atomic Layer Deposition), and the like have been developed as a process for forming a film in a fine hole. The ALD method is characterized in that a film can be grown conformally even in a fine hole having a high aspect ratio because the film is grown for each monoatomic layer.

Non-Patent Documents 1 and 2 report that a TiO ₂ film or an HfO ₂ film formed by the ALD method exhibits a resistance change phenomenon by an electric pulse.

  In Patent Document 2, since a dense film with a small film thickness and few defects can be formed, the resistance change using a NiO thin film formed by the ALD method is expected in order to improve the resistance change characteristic with a small leakage current. Type nonvolatile memory element is proposed.

  Patent Document 3 discloses a resistance change element including two resistance change layers having different oxygen contents.

  Further, Patent Document 4 discloses a resistance change element using an oxynitrogen deficient tantalum oxynitride as a resistance change element. The oxygen content ratio of oxygen to nitrogen in the oxynitrogen-deficient tantalum oxynitride layer is 1.08 to 1.35.

International Publication No. 2008/47711 JP 2007-84935 A International Publication No. 2008/149484 International Publication No. 2008/146461

Journal Of Applied Physics, 2005, 98, 033715 Japan Journal Of Applied Physics 2007 Volume 46 No. 4B 2172-2174

  However, when a nonvolatile memory device is formed using the resistance change layer disclosed in Patent Document 3, the following problems arise. In the manufacturing process of the nonvolatile memory device, the resistance variable element is subjected to heat treatment in steps such as formation of an interlayer insulating film, plug formation, wiring formation, and recovery annealing at the time of forming a multilayer wiring. By these heat treatments, oxygen diffuses from the second tantalum oxide layer having a high oxygen concentration into the first tantalum oxide layer having a low oxygen concentration in the variable resistance layer of the variable resistance element. As a result, the oxygen concentration profile is degraded. Occurs.

  Further, when two resistance change layers having different oxygen contents are embedded in the hole, unlike the ordinary stacked structure, the two resistance change layers having different oxygen contents are added to the bottom of the hole directly above the lower electrode film. Since both layers are in contact with each other on the side wall of the hole, the bottomed cylinder is formed, and the area of the interface is remarkably increased.

  The present invention solves the above-described conventional problem, and can suppress mutual diffusion between the first variable resistance layer and the second variable resistance layer, and the nonvolatile memory in which the operation of the storage device is stable. An object is to provide an apparatus.

One aspect of the nonvolatile memory device according to the present invention includes a first electrode wiring formed in a strip shape on a substrate, the first electrode wiring and an interlayer insulating layer formed on the substrate, and the interlayer insulation. A memory cell hole extending through the layer to reach the first electrode wiring; a resistance change layer formed in a region covering the bottom and side surfaces of the memory cell hole in the memory cell hole; The first electrode formed in the memory cell hole and a direction intersecting the first electrode wiring in a region covering at least the opening of the memory cell hole on the first electrode and the insulating layer A first wiring formed in a strip shape, wherein the variable resistance layer includes a first variable resistance layer made of an oxygen-deficient transition metal oxide, and an oxygen content ratio of the first variable resistance layer Different A laminated structure of the second variable resistance layer comprised of acid nitrogen deficient transition metal oxynitride, wherein the transition metal M, the first composition of the resistance variable layer MO _z, the second variable resistance layer Is expressed as MO _x N _y , the relationship z> (x + y) is satisfied.

  Even if the area of the interface portion between the two resistance change layers increases due to the structure in which the two resistance change layers having different oxygen contents are embedded in the holes, the nonvolatile memory device of the present invention Since the metal oxynitride is deficient in oxynitrogen, it is possible to suppress mutual diffusion with the metal oxide that is the first variable resistance layer, and the operation of the memory device is stabilized.

FIG. 1 is a plan view showing an example of the configuration of the nonvolatile memory device according to the first embodiment of the present invention and a sectional view taken along line 1A-1A. 2 is a plan view showing an example of the configuration of the variable resistance element, which is the main part of FIG. 1, and a cross-sectional view taken along line 2A-2A. FIG. 3 is a cross-sectional view in one manufacturing process of the nonvolatile memory device according to the first embodiment of the present invention. FIG. 4 is a plan view in one manufacturing process of the nonvolatile memory device according to the first embodiment of the present invention, and a sectional view taken along line 3A-3A. FIG. 5 is a cross-sectional view in one manufacturing process of the nonvolatile memory device according to the first embodiment of the present invention. FIG. 6 is a cross-sectional view in one manufacturing process of the nonvolatile memory device according to the first embodiment of the present invention. FIG. 7 is a cross-sectional view in one manufacturing process of the nonvolatile memory device according to the first embodiment of the present invention. FIG. 8 is a plan view and a cross-sectional view in one manufacturing process of the nonvolatile memory device according to the first embodiment of the present invention. FIG. 9 is a plan view and a cross-sectional view in one manufacturing process of the nonvolatile memory device according to the first embodiment of the present invention. FIG. 10 is a diagram showing the relationship between the (O + N) ratio in the TaO _x N _y film and the specific resistance. FIG. 11 is a cross-sectional view of a planar element whose resistance change characteristics are measured. FIG. 12 is a diagram showing resistance change characteristics when a pulse is applied to the planar element. FIG. 13 is a diagram showing resistance change characteristics when a pulse is applied to the planar element. FIG. 14 is a diagram showing resistance change characteristics when a pulse is applied to the planar element. FIG. 15 is a cross-sectional view showing an example of the configuration of the nonvolatile memory device according to the second embodiment of the present invention. FIG. 16: is sectional drawing which shows an example of a structure of the resistance change element which concerns on the modification of 2nd Embodiment of this invention. FIG. 17 is a cross-sectional view showing an example of the configuration of the nonvolatile memory device according to Embodiment 3 of the present invention. FIG. 18 is a plan view and a cross-sectional view taken along the line A-A ′ for explaining the areas of the interface portions of the plurality of variable resistance layers in the planar element. FIG. 19 is a plan view and a cross-sectional view taken along line B-B ′ for explaining the areas of the interface portions of the plurality of resistance change layers in the Hall element.

One aspect of the nonvolatile memory device according to the present invention includes a first electrode wiring formed in a strip shape on a substrate, the first electrode wiring and an interlayer insulating layer formed on the substrate, and the interlayer insulation. A memory cell hole extending through the layer to reach the first electrode wiring; a resistance change layer formed in a region covering the bottom and side surfaces of the memory cell hole in the memory cell hole; The first electrode formed in the memory cell hole and a direction intersecting the first electrode wiring in a region covering at least the opening of the memory cell hole on the first electrode and the insulating layer A first wiring formed in a strip shape, wherein the variable resistance layer includes a first variable resistance layer made of an oxygen-deficient transition metal oxide, and an oxygen content ratio of the first variable resistance layer Different A laminated structure of the second variable resistance layer comprised of acid nitrogen deficient transition metal oxynitride, wherein the transition metal M, the first composition of the resistance variable layer MO _z, the second variable resistance layer Is expressed as MO _x N _y , the relationship z> (x + y) is satisfied.

  Here, the first variable resistance layer may be in contact with the bottom and side surfaces of the memory cell hole, and the second variable resistance layer may be in contact with the first variable resistance layer.

  The transition metal is preferably any one transition metal selected from the group consisting of tantalum, hafnium, zirconium, nickel, and titanium. The transition metal is preferably tantalum.

  The total number of oxygen atoms and nitrogen atoms in the oxynitrogen-deficient tantalum oxynitride is preferably 50 to 70 atm%.

  In addition, a configuration in which a first current control layer is disposed between the first electrode and the first wiring may be employed.

  As a structure and manufacturing method for realizing a fine memory element, 1) a method of laminating and forming a necessary electrode layer and a resistance change layer on a surface parallel to a substrate, and then collectively processing by a dry etching process; 2) A method of forming a fine hole in advance and embedding a variable resistance layer or an electrode in the fine hole is conceivable.

  In the case of 1), the film forming process is easy. However, since a plurality of thin film materials having different etching rates are collectively dry-etched, it is not easy to process with a desired accuracy. In particular, in the case of an element structure with a large number of stacked layers or when the element size is small, the etching process becomes difficult.

  On the other hand, in the case of 2), it becomes more difficult to form the variable resistance layer and the electrode in the fine hole than the problem of the etching process. In general, it is difficult to form a film with good coverage in a fine hole having a high aspect ratio by a film forming process using a physical method such as sputtering. Therefore, a CVD method or an ALD method is used.

  In a Hall element formed by embedding a plurality of variable resistance layers with different oxygen contents in fine holes, a plurality of variable resistance layers are stacked in parallel to the main surface of the substrate in the same footprint as the Hall type element. Compared with the planar type element formed, the contact area between the resistance change layers becomes large. For example, consider a planar type element and a Hall type element that can be formed in a square footprint with one side of Lnm.

  FIG. 18 is a plan view schematically showing an example of a planar element and a cross-sectional view taken along the line A-A ′. In the case of such a planar element, the contact area S between the resistance change layers is expressed by (Expression 1).

S = L ² (Formula 1)

FIG. 19 is a plan view schematically showing an example of the Hall element and a sectional view taken along the line BB ′. In the case of such a Hall-type element, assuming that the hole depth is D, the thickness of the first resistance change layer is T ₁ , and the thickness of the second resistance change layer is T ₂ , the contact area between the resistance change layers. S is represented by (Formula 2).

S = (L−2T ₁ ) × (D−T ₁ ) π + {(L−2T ₁ ) / 2} ² π (Expression 2)

For example, considering the case of L = 60 nm, D = 120 nm, and T ₁ = T ₂ = 10 nm, in the planar type element, the contact area S between the resistance change layers is 3600 nm ² from Equation 1. On the other hand, in the Hall element, the contact area S between the resistance change layers is 15079.6 nm ² from Equation ² , which is about 4.2 times that of the laminated structure. Therefore, it is estimated that the amount of oxygen interdiffusion between the resistance change layers also increases.

  Metal oxynitrides such as tantalum (Ta) and titanium (Ti) are stable compounds and have high barrier properties like tantalum nitride (TaN) and titanium nitride (TiN). Further, it is considered that the metal oxynitride substitutes a part of nitrogen atoms in the metal nitride with oxygen atoms. For this reason, it is considered that the diffusion of oxygen atoms from the interface is suppressed because the sites substituted with oxygen after diffusion are limited.

  Therefore, it is considered that the diffusion of oxygen atoms from the interface has an effect of suppressing the substitution site after diffusion, and oxygen diffusion can be prevented. Therefore, in the configuration of the nonvolatile memory device of the present invention, even if the area of the interface portion between the two resistance change layers increases due to the structure in which the two resistance change layers having different oxygen contents are embedded in the holes, Since the variable resistance layer is an oxynitrogen-deficient metal oxynitride, mutual diffusion with the metal oxide that is the first variable resistance layer can be suppressed.

When the composition of the first resistance change layer is expressed as MO _z and the composition of the second resistance change layer is expressed as MO _x N _y ,
z> (x + y) (Formula 3)
Satisfies the relationship. By satisfying the relationship of Equation 3, the resistivity of the tantalum oxide layer that is the first variable resistance layer becomes higher than the resistivity of the oxynitrogen-deficient tantalum oxynitride layer.

  The voltage pulse applied during the resistance change operation is distributed to both the tantalum oxide layer, which is the first resistance change layer, and the oxynitrogen deficient tantalum oxynitride layer, which is the second resistance change layer. It is a component distributed to the tantalum oxide layer through which oxygen enters and exits that contributes to the operation. By making the resistivity of the tantalum oxide layer higher than the resistivity of the oxynitride-deficient tantalum oxide layer, the voltage pulse component distributed to the tantalum oxide layer increases, and the nonvolatile memory device operates at a low voltage. It becomes possible to make it.

Further, by satisfying the above compositional relationship, the resistivity of the MO _z layer that is the first variable resistance layer becomes higher than the resistivity of the MO _x N _y layer that is the second variable resistance layer. The voltage pulse applied during the resistance change operation is applied to both the first resistance change layer and the second resistance change layer. Of these, the resistance change operation contributes to the first resistance change layer where oxygen enters and exits. This is the applied voltage. By making the resistivity of the first resistance change layer higher than the resistivity of the second resistance change layer, the component of the voltage pulse distributed to the first resistance change layer is changed to the voltage pulse distributed to the second resistance change layer. Larger than the ingredients. As a result, the nonvolatile memory device can be operated at a lower voltage than in the case where the variable resistance layer is formed of a single layer. When the nonvolatile memory device has the above-described configuration, the voltage necessary for the resistance change operation of the nonvolatile memory device is 2.4 V or less, and the nonvolatile memory device can be operated at a low voltage.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected about the same element and description may be abbreviate | omitted. Further, the shapes of the transistors, the memory portions, and the like are schematic, and the numbers thereof are easily illustrated.

(First embodiment)
[Device configuration]
FIG. 1 is a plan view schematically showing an example of the configuration of the nonvolatile memory device 10 according to the first embodiment of the present invention, and a cross-sectional view taken along the line 1A-1A in the arrow direction. The plan view of FIG. 1 shows a virtual state in which a part of the uppermost fourth interlayer insulating layer 23 is removed for easy understanding.

  FIG. 2 is a plan view of the first variable resistance element 17 which is the main part of FIG. 1, and a cross-sectional view taken along the line 2A-2A in the direction of the arrow.

  The nonvolatile memory device 10 according to this embodiment includes a substrate 11, a first backing wiring 15 formed on the substrate 11, and a first backing wiring 15 formed on the first backing wiring 15 so as to be in physical contact therewith. A lower layer wiring composed of one electrode wiring 151 and a third interlayer insulating layer 16 formed so as to cover the lower layer wiring are provided. The lower layer wiring is formed in a band shape when viewed from a direction perpendicular to the main surface of the substrate 11 (hereinafter referred to as a thickness direction of the substrate).

  In the third interlayer insulating layer 16, memory cell holes 29 reaching the first electrode wiring 151 are formed at a predetermined interval. Corresponding to the memory cell hole 29, the first resistance variable element 17 is formed.

  Here, the first electrode wiring 151 is a belt-like electrode and constitutes the first electrode of the first resistance change element 17. The first backing wiring 15 is made of a material having substantially the same shape as the first electrode wiring 151 and having a lower resistance than the first electrode wiring 151 in order to reduce the wiring resistance of the first electrode wiring 151 that is a strip-shaped electrode. Wiring.

  Within the memory cell hole 29, conformal (conformal) is formed with substantially the same thickness according to the shape of the memory cell hole 29 so as to cover the bottom and side walls of the memory cell hole 29 and to be in physical contact with the first electrode wiring 151. And a second resistance change layer 18b formed so as to cover the bottom and side walls of the first resistance change layer 18a and to be in physical contact with the first resistance change layer 18a, A first electrode 19 formed so as to be in physical contact with the second resistance change layer 18b is formed inside the second resistance change layer 18b. Here, the term “conformal” means that the shape adaptability is good, and the first resistance change layer 18a can be formed with substantially the same film thickness without any gap between the bottom surface and the side wall in the memory cell hole 29 and without stepping. Define.

  For each memory cell hole 29, the first electrode wiring 151 exposed at the bottom of the memory cell hole 29, the first resistance change layer 18 a inside the memory cell hole 29, and the second electrode inside the memory cell hole 29 The variable resistance layer 18 b and the first electrode 19 inside the memory cell hole 29 constitute the first variable resistance element 17.

  The first resistance change layer 18a is preferably made of a transition metal oxide, more preferably an oxygen-deficient tantalum oxide. The second resistance change layer 18b is preferably made of an oxynitrogen-deficient metal oxynitride, more preferably an oxynitrogen-deficient tantalum oxynitride.

Here, the oxygen-deficient transition metal oxide refers to an oxide of transition metal M by MO _x (x is a composition ratio represented by the number of moles of oxygen O when transition metal M is 1 mol) and In the case of the notation, it is an oxide smaller than the composition ratio in which the composition ratio x of oxygen O is stoichiometrically stable (2.5 when the transition metal M is tantalum Ta).

In addition, the oxynitride-deficient metal oxynitride is an oxynitride of the transition metal M that is MO _x N _y (where x and y are the respective moles of oxygen O and nitrogen N when the transition metal M is 1 mol). (Composition ratio expressed by a number), the sum of the composition ratio x of oxygen O and the composition ratio y of nitrogen N is stoichiometrically stable (the transition metal M is tantalum). In the case of Ta, the oxide is smaller than 2.5).

For example, oxynitrogen-deficient tantalum oxynitride is defined as follows. In general, it is stable that tantalum is present as +5 valence, oxygen as -2 valence, and nitrogen as -3 valent ion. Therefore, when the composition of the oxynitrogen-deficient tantalum oxynitride is represented by TaO _x N _y , an oxy-nitrogen deficient tantalum oxynitride satisfying 2x + 3y = 5 can exist stably. The oxynitrogen deficient tantalum oxynitride is an oxynitrogen deficient tantalum oxynitride having a composition such that 2x ′ + 3y ′ <5 when the composition is represented by TaO _{x ′} N _{y ′} .

  By using a resistance change layer of a transition metal oxide composed of an oxygen-deficient tantalum oxide, a nonvolatile memory element using a resistance change phenomenon having reversibly stable rewriting characteristics can be obtained. This is described in detail in Patent Document 5: International Publication No. 2008/059701.

  Further, the oxynitrogen-deficient tantalum oxynitride layer is less likely to diffuse oxygen than the first tantalum oxide layer described in International Publication No. 2008/149484 of Patent Document 3. This is because the metal oxynitride of Ta is a stable compound and has a high barrier property like TaN. Further, it is considered that the metal oxynitride substitutes a part of nitrogen atoms in the metal nitride with oxygen atoms. For this reason, it is considered that the diffusion of oxygen atoms from the interface is suppressed because the sites substituted with oxygen after diffusion are limited.

  As described above, it is possible to suppress the diffusion of oxygen from the tantalum oxide layer, and it is possible to reduce the deterioration of the oxygen concentration profile accompanying the increase in the interface layer area, which was a problem of the Hall resistance variable element. It becomes.

  The first resistance change layer 18a and the second resistance change layer 18b include not only tantalum oxide and tantalum oxynitride, but also transitions such as titanium (Ti), hafnium (Hf), zirconium (Zr), or nickel (Ni). You may form with the metal based oxide and oxynitride. Such a transition metal oxide exhibits a specific resistance value when a voltage or current exceeding a threshold value is applied, and the resistance value is newly applied until a pulse voltage or pulse current having a certain magnitude is applied. In order to keep the resistance value, it can be used for a nonvolatile memory element.

The oxygen content of the first resistance change layer 18a is preferably higher than the oxygen content of the second resistance change layer 18b. That is, when the transition metal oxide constituting the first resistance change layer 18a is MO _z and the transition metal oxynitride constituting the second resistance change layer 18b is MO _x N _y ,
z> (x + y) (Formula 4)
It is preferable that Here, in particular, x> 0 and y> 0 may be satisfied. The variable resistance element in which the variable resistance layer is composed of two layers having different oxygen contents is described in detail in International Publication No. 2008/149484 of Patent Document 3.

  By setting the oxygen content of the resistance change layer high in the vicinity of the first electrode wiring 151, it is possible to easily develop a resistance change phenomenon due to an oxidation-reduction reaction at the interface between the first electrode wiring 151 and the resistance change layer. it can. As a result, good memory cell characteristics capable of low voltage driving can be obtained.

  The first electrode wiring 151 is preferably composed of platinum, iridium, palladium, or the like. The standard electrode potential of platinum or iridium is +1.2 eV, and the standard electrode potential of palladium is +1.0 eV. In general, the standard electrode potential is one index of the degree of oxidization, and if this value is large, it means that it is difficult to oxidize, and if it is small, it means that it is easily oxidized.

  According to the inventors' research, the greater the difference between the standard electrode potential of the material constituting the electrode and the standard electrode potential of the transition metal contained in the resistance change layer, the easier the resistance change occurs. It has become clear that changes are unlikely to occur. From this fact, it is presumed that the ease of oxidation of the material of the electrode and the resistance change layer plays a major role in the mechanism of the resistance change phenomenon.

  The standard electrode potential of tantalum is −0.6 eV, which is lower than the standard electrode potential of platinum, iridium, and palladium. Therefore, in the above preferred configuration, an oxidation-reduction reaction occurs at the interface between the first electrode wiring 151 made of platinum, iridium, and palladium and the first resistance change layer 18a made of tantalum oxide, so that oxygen is exchanged. As a result, a resistance change phenomenon occurs.

  The first backing wiring 15 can be composed of, for example, a Ti—Al—N alloy, Cu, Al, Ti—Al alloy, or a laminated structure thereof. The first electrode wiring 151 can be composed of Pt, Ir, or the like. The first backing wiring 15 and the first electrode wiring 151 can be easily formed by performing an exposure process and an etching process after forming the film by sputtering.

  The first electrode 19 is preferably made of a material having a standard electrode potential lower than that of the material constituting the first electrode wiring 151. Furthermore, the first electrode 19 is preferably made of a material having a standard electrode potential lower than that of the transition metal constituting the resistance change layer. With such a configuration, the oxidation-reduction reaction of the first resistance change layer 18a selectively occurs in the vicinity of the interface between the first electrode wiring 151 and the first resistance change layer 18a, thereby causing a stable resistance change. it can.

  The first electrode 19 may be made of a transition metal nitride constituting the first resistance change layer 18a and the second resistance change layer 18b. For example, when the resistance change layer 18a and the second resistance change layer 18b are made of tantalum oxide, the first electrode 19 may be made of tantalum nitride (TaN) or aluminum.

  In the upper opening of the memory cell hole 29, the first resistance change layer 18a, the second resistance change layer 18b, and the first electrode 19 are exposed, and a first wiring 22 is formed so as to cover them. The The first wiring 22 is a band-shaped memory cell in a direction intersecting the first backing wiring 15 in a plane parallel to the main surface of the substrate and different from the plane where the first backing wiring 15 is disposed. It is formed on the third interlayer insulating layer 16 so as to have a shape (area) larger than the opening of the hole 29, completely covering the opening of the memory cell hole 29 and protruding to the periphery thereof.

  As a material of the first wiring 22, a low resistance material such as copper (Cu) or aluminum (Al) can be used.

  As shown in FIG. 1, the first wiring 22 extends to the outside of the region where the first variable resistance element 17 is formed in a matrix. In the matrix region, the first wiring 22 functions as a wiring (word line or bit line) connecting each memory cell.

  In the present embodiment, a silicon single crystal substrate is used as the substrate 11, and a semiconductor circuit having active elements 12 such as transistors integrated on the substrate 11 is provided. In FIG. 1, the active element 12 is a transistor (MOS-FET) including a source region 12a, a drain region 12b, a gate insulating film 12c, and a gate electrode 12d. However, not only the active element 12 but also an element generally required for a memory circuit such as a DRAM can be formed on the substrate 11.

  The first backing wiring 15 and the first wiring 22 are active elements 12 in a region (for example, the periphery of the matrix region) different from the matrix region in which the first resistance change element 17 is formed as viewed from the thickness direction of the substrate 11. Are connected to each.

  That is, in FIG. 1, the first backing wiring 15 includes the second buried conductor 24, the first buried conductor 25, and the circuit wiring in the memory cell holes formed in the first interlayer insulating layer 13 and the second interlayer insulating layer 14. 26 is connected to the source region 12 a of the active element 12. The first wiring 22 is similarly connected to another active element (not shown) via the third buried conductor 28. The active element 12 may be disposed under the matrix region.

As the first interlayer insulating layer 13, the second interlayer insulating layer 14, the third interlayer insulating layer 16, and the fourth interlayer insulating layer 23, an insulating oxide or nitride can be used. Specifically, a TEOS-SiO film or a silicon nitride (SiN) film formed by CVD using silicon oxide (SiO) or ozone (O ₃ ) and tetraethoxysilane (TEOS) by CVD is used. it can. The first interlayer insulating layer 13 and the second interlayer insulating layer 14 are made of fluorine-containing oxide (for example, SiOF), carbon-containing nitride (for example, SiCN), or organic resin (for example, for reducing parasitic capacitance between wirings). , Polyimide). As the third interlayer insulating layer 16, a silicon carbonitride (SiCN) film, a silicon carbonate (SiOC) film, or a silicon fluorine oxide (SiOF) film, which is a low dielectric constant material, may be used.

  The circuit wiring 26 may be formed of aluminum as in the prior art, but is preferably formed of copper that can realize low resistance even when miniaturized.

[Production method]
Next, a method for manufacturing the nonvolatile memory device according to the first embodiment of the present invention will be described using the example of the nonvolatile memory device 10 described above.

  FIG. 3 shows the non-volatile state after the step of forming the second interlayer insulating layer 14, the first backing wiring 15, the first electrode wiring 151, and the third interlayer insulating layer 16 on the substrate 11 on which the active element 12 is formed. 3 is a cross-sectional view of the storage device 10. FIG.

  FIG. 4 is a plan view of the nonvolatile memory device 10 after the step of forming the memory cell holes 29 in the third interlayer insulating layer 16 and a cross-sectional view taken along the line 3A-3A from the arrow direction. 4 to 9 including the cross-sectional view of FIG. 4 are all cross-sectional views of the nonvolatile memory device 10 taken along the line 3A-3A in each step, as viewed from the direction of the arrows.

  FIG. 5 is a cross-sectional view of the nonvolatile memory device 10 after the step of forming the first variable resistance material layer 181a to be the first variable resistance layer 18a on the third interlayer insulating layer 16 and inside the memory cell hole 29. It is.

  FIG. 6 is a cross-sectional view of the nonvolatile memory device 10 after the step of forming the second variable resistance material layer 181b to be the second variable resistance layer 18b on the first variable resistance material layer 181a.

  FIG. 7 is a cross-sectional view of the nonvolatile memory device 10 after the step of forming the first electrode material layer 191 to be the first electrode 19 on the second variable resistance material layer 181b.

  8 leaves the first variable resistance material layer 181a, the second variable resistance material layer 181b, and the first electrode material layer 191 inside the memory cell hole 29, and the other first variable resistance material layer 181a and the second variable resistance material layer 181a. 6A is a plan view and a cross-sectional view of the nonvolatile memory device 10 after a step of removing the variable resistance material layer 181b and the first electrode material layer 191 by CMP. FIG.

  FIG. 9 is a plan view and a cross-sectional view of the non-volatile memory device 10 after the step of laminating the first wiring 22 so as to completely cover the upper opening of the memory cell hole 29 and protrude outside thereof.

  Hereinafter, a method for manufacturing the nonvolatile memory device 10 according to this embodiment will be described with reference to FIGS.

  First, as shown in FIG. 3, a plurality of active elements 12, a first interlayer insulating layer 13, a second interlayer insulating layer 14, a second embedded conductor 24, a first embedded conductor 25, a circuit, The wiring 26, the first backing wiring 15, the first electrode wiring 151, and the third interlayer insulating layer 16 are formed.

  In particular, the first backing wiring 15 and the first electrode wiring 151 may be embedded in the second interlayer insulating layer 14. Such a configuration is formed as follows, for example.

  That is, the second interlayer insulating layer 14 is connected to the circuit wiring 26 and the groove for embedding the first backing wiring 15 and the first electrode wiring 151 by using a technique used in a general semiconductor process. A memory cell hole is formed. These grooves are formed in a band shape when viewed from the thickness direction of the substrate.

  After these trenches and memory cell holes are formed, the conductors to be the first backing wiring 15 and the first electrode wiring 151 are buried by the CVD method or the like, and then unnecessary portions are removed by, for example, CMP.

  In other steps for forming the structure of FIG. 3, a well-known manufacturing method can be used, and detailed description thereof is omitted.

  Next, as shown in FIG. 4, the memory cell holes 29 are formed in the third interlayer insulating layer 16 covering the first electrode wiring 151 at a constant arrangement pitch so that the first electrode wiring 151 is exposed on the bottom surface. Form. As can be seen from the plan view of FIG. 4, the memory cell hole 29 has an outer shape smaller than the width of the first backing wiring 15. In the figure, the memory cell hole 29 is rectangular, but it may be circular, elliptical, or another shape.

  Since the memory cell hole 29 can be formed by a general semiconductor process, detailed description thereof is omitted.

  Next, as shown in FIG. 5, a first variable resistance material layer 181a (first deposited film) to be the first variable resistance layer 18a is formed on the third interlayer insulating layer 16 in which the memory cell holes 29 are formed. Form. In this embodiment, the first variable resistance material layer 181a is formed by depositing tantalum oxide on the inside (side wall and bottom) of the memory cell hole 29 and on the third interlayer insulating layer 16 by the CVD method. The

  In this embodiment, a CVD method is used as a method for forming the first variable resistance material layer 181a. For the formation of the first variable resistance material layer 181a, as another film formation method, a sputtering method or an ALD method suitable for a conformal film formation in a fine hole may be used. By this process, the first variable resistance material layer 181a is conformally formed with a substantially uniform thickness inside the memory cell hole 29 (side wall and bottom).

As the source gas, for example, tertiary butylimide trisdiethylamide tantalum ((CH ₃ ) ₃ CNTa [N (C ₂ H ₅ ) ₂ ] ₃ , hereinafter referred to as TBTDET) shown in (Chemical Formula 1) can be used.

For example, ozone (O ₃ ) gas is used as the reactive gas. After film formation, nitrogen (N ₂ ) gas is used as a purge gas. However, the kind of gas is not limited to the above.

  In the method for forming the first resistance change material layer 181a in the present embodiment, first, the material container is filled with TBTDET which is a material (precursor) of the resistance change layer. A substrate heated to a temperature (for example, 325 ° C.) at which self-decomposition reaction of the source gas occurs is held inside the film formation chamber. Note that experiments were performed under a plurality of temperature conditions of 325 ° C., 350 ° C., 400 ° C., and 440 ° C. as the substrate heating temperature.

The TBTDET of the raw material container is heated to 100 ° C., and this is bubbled with nitrogen gas as a carrier gas to generate a source gas, and the source gas is introduced into the deposition chamber. At the same time, O ₃ gas generated by an ozonizer as a reactive gas is introduced into the film forming chamber. Thereby, TBTDET is oxidized to form a Ta oxide layer, and a ligand contained in TBTDET is oxidized to a by-product such as CO ₂ and removed.

  After the desired thickness of Ta oxide is formed, nitrogen gas is introduced into the chamber and the chamber gas is purged to remove excess reactive gas and by-products.

  Next, as shown in FIG. 6, the second variable resistance layer 18 b is formed on the side wall and bottom of the memory cell hole 29 and on the first variable resistance material layer 181 a formed on the third interlayer insulating layer 16. A second variable resistance material layer 181b (second deposited film) is formed.

  In the present embodiment, tantalum oxynitride is used as the first variable resistance material layer on the inside (side wall and bottom) of the memory cell hole 29 ′ in which the first variable resistance material layer 181 a is formed and on the third interlayer insulating layer 16. A second variable resistance material layer 181b is formed on the layer 181a by deposition by a CVD method.

  In the present embodiment, a continuous process of a CVD method and an oxidation process is used as an example of a method for forming the oxynitrogen-deficient metal oxynitride thin film that is the second variable resistance material layer 181b.

Specifically, the forming method includes, for example, a first step of introducing a source gas containing a transition metal atom and a reactive gas, a second step of purging the source gas and the reactive gas after the first step, It consists of a third step in which an oxidizing reactive gas such as O ₃ or O ₂ is introduced after two steps.

  In the first step, a metal nitride thin film is first formed using a nitriding reactive gas. Except that the reactive gas species are different, conditions such as the film formation temperature are the same as the formation of the first variable resistance material layer 181a. Therefore, description of the parts common to both is omitted.

In the third step, an oxidizing reactive gas such as O ₃ or O _{2 is} introduced for a certain period of time while maintaining the substrate temperature at 350 ° C., which is the same as that in the first and second steps. The metal oxynitride thin film is formed by substituting nitrogen with oxygen.

  Note that the composition of the metal oxynitride can be controlled by repeating the first step, the second step, and the third step not only once but a plurality of times.

  The principle that the layer is formed even when an oxide or oxynitride containing hafnium, zirconium, nickel, or titanium as a base metal is used as the transition metal oxide or transition metal oxynitride constituting the resistance change layer. In view of the above, it is presumed that metal oxides having different oxygen contents can be formed as in the case of tantalum oxide and tantalum oxynitride.

The raw material (precursor) of the resistance change layer in this case is zirconium chloride [ZrCl ₄ ], tetra (ethylmethylamino) hafnium [Hf (NCH ₃ C ₂ H ₅ ) ₄ ], nickel 1-dimethylamino-2methyl -2 butanolate [Ni (C ₇ H ₁₆ NO)], tetraethoxy titanium [Ti (OC ₃ H ₇ ) ₄ ] and the like can be used.

  Thereafter, as shown in FIG. 7, the first electrode material layer 191 is formed on the second variable resistance material layer 181b.

  In the present embodiment, tantalum nitride (TaN) is used for the first resistance change inside the memory cell hole 29 ″ (side wall and bottom) in which the second variable resistance material layer 181b is formed and on the third interlayer insulating layer 16. A first electrode material layer 191 is formed on the second variable resistance material layer 181b on the material layer 181a by depositing, for example, by an ALD method or a CVD method.

Since the specific method of the CVD method is the same as that in the first variable resistance material layer 181a or the second variable resistance material layer 181b, detailed description thereof is omitted. As a raw material (precursor), or the like can be used TBTDET or _{TaCl 5, Ta (OC 2 H} 5) 5. A nitriding gas can be used as the reactive gas.

  Next, as shown in FIG. 8, the surface of the third interlayer insulating layer 16 of the first electrode material layer 191, the second variable resistance material layer 181b, and the first variable resistance material layer 181a is covered using a CMP process. The portion and the portion above the upper opening of the memory cell hole 29 (the portion whose height from the substrate is higher than the upper end surface of the third interlayer insulating layer 16) are removed. Thus, the first variable resistance layer 18a, the second variable resistance layer 18b, and the first electrode 19 are embedded in the memory cell hole 29.

  Next, as shown in FIG. 9, the first wiring 22 is formed so as to be connected to the first electrode 19. As a specific forming method, a well-known technique can be used, and thus detailed description thereof is omitted.

  The first wiring 22 has a shape (area) at least larger than the opening of the memory cell hole 29 when viewed from the thickness direction of the substrate so as to completely cover the memory cell hole 29 on the third interlayer insulating layer 16. The first backing wiring 15 and the first electrode wiring 151 are formed in a strip shape in a direction intersecting with the first backing wiring 15 and the first electrode wiring 151. The first wiring 22 is formed so as to extend outside the region where the first variable resistance element 17 is formed in a matrix. A third buried conductor 28 is formed simultaneously with the first wiring 22, and is connected to a circuit wiring (not shown) via the third buried conductor 28, and electrically connected to an active element provided at a position not shown. Connecting.

  Further, by forming the fourth interlayer insulating layer 23 so as to cover the third interlayer insulating layer 16 and the first wiring 22, a nonvolatile memory device as shown in FIG. 1 can be obtained.

[Characteristics of oxynitrogen-deficient tantalum oxynitride layer]
Next, the relationship between the composition and specific resistance of the oxynitrogen-deficient tantalum oxynitride thin film formed as the second variable resistance material layer 181b will be described.

  FIG. 10 shows O + N (total number of oxygen atoms and nitrogen atoms) in the oxynitrogen-deficient tantalum oxynitride thin film (containing residual C derived from TBTDET) formed by a continuous process of CVD and oxidation. 2 shows the relationship between the atm% value and the specific resistance of the oxynitride-deficient tantalum oxynitride thin film. The composition analysis was performed by Rutherford backscattering (RBS) method. The oxygen content contained in the oxynitrogen-deficient tantalum oxynitride thin film formed using the above-described method is considered to depend on the oxidation treatment conditions (oxidizing gas flow rate, time) after film formation by the CVD method.

  The composition of oxygen and nitrogen analyzed by the RBS method includes a relatively large error of ± 4% in units of atm%. For this reason, an error also occurs in the atm% value of O + N. Considering the error due to the RBS method, the atm% value of O + N is in the range of 50 to 70. FIG. 10 also plots the relationship between the atm% value of O and the specific resistance in a tantalum oxide film formed by sputtering as a comparative example (that is, equivalent to N atm% value = 0). .

  From FIG. 10, the correlation between the film composition and the specific resistance has the same tendency between the oxynitride-deficient tantalum oxynitride thin film formed by the CVD method and the tantalum oxide film formed by the sputtering method. It can be confirmed that the specific resistance value of the film increases as the atm% value of O + N increases.

  The solid line in FIG. 10 shows the results of measuring the sheet resistance value of the tantalum oxynitride layer, which is the second variable resistance layer formed at a substrate temperature of 400 ° C. and a film thickness of 50 nm, by the four-terminal measurement method, and obtaining the specific resistance. Show.

  Here, the point a is analyzed as Ta / O / N / C = 33.6 / 0 / 54.5 / 11.9 (atm%) after film formation by CVD and before oxidation treatment. The specific resistance of each sample is shown. Note that the analysis result of O atm% = 0 is not considered to contain O at all even though it is before the oxidation treatment, so an error due to low analytical sensitivity for O of less than 4 atm%. It is seen.

The point b was analyzed as Ta / O / N / C = 32.4 / 4.7 / 54.3 / 8.6 (atm%) (TaO _0.15 N _1.68 ). ) Indicates the specific resistance of the sample, and the point c was analyzed as the composition Ta / O / N / C = 29.9 / 7.4 / 54.2 / 8.5 (atm%) (TaO _0.25 N is the specific resistance of the sample (denoted as _1.81 ).

  The specific resistance of the tantalum oxide material layer indicated by the one-dot chain line in FIG. 10 was calculated from the film thickness measured by the cross-sectional SEM and fluorescent X-ray and the sheet resistance value measured by the four-terminal measurement method.

  Next, FIG. 11 shows an operation example as a memory having a laminated structure of the first resistance change layer and the second resistance change layer of the present application, that is, an operation example in the case of writing / reading information. It confirmed with the planar type | mold element.

Planar element for characterization is on the silicon substrate 200 SiN film (thickness 100 nm) was formed, by _TaO x _{N y} film formed by the lower electrode 205, CVD method configured in TaN (film thickness 30 nm) there second variable resistance layer 206 b, TaO _z film laminated first variable resistance layer 206a is (thickness 5 nm), an upper electrode (thickness 50 nm) 207 is Ir film formed by a sputtering method successively formed by sputtering It is made by doing. The first variable resistance layer 206a and the second variable resistance layer 206b constitute the variable resistance layer 206. The lower electrode 205 and the upper electrode 207 are connected to wirings 201 and 211 via contact plugs 204 and 210, respectively.

According to such a method, a device A including a TaO _x N _y film formed at a substrate temperature of 325 ° C. and analyzed to have a composition of x = 0.31 and y = 1.41 is formed at a substrate temperature of 400 ° C. Is formed at a substrate temperature of 400 ° C. and a device B including a TaO _x N _y film (corresponding to the sample at point b in FIG. 10) analyzed as x = 0.15 and y = 1.68. A device C including a TaO _x N _y film (corresponding to a sample at point c in FIG. 10) analyzed to be = 0.25 and y = 1.81 was manufactured, and operation characteristics of each device were evaluated.

  FIG. 12 is a diagram showing a resistance change characteristic when the pulse of the element A is applied. As shown in FIG. 12, by applying two types of voltage pulses having different polarities, the element A changes between a high resistance state and a low resistance state. That is, when a negative voltage pulse (voltage -1.5 V, pulse width 100 ns) is applied to the upper electrode 207 with the lower electrode 205 as a reference, the element A changes from a high resistance state (resistance value of about 150,000 Ω) to a low resistance state ( The resistance value changes to about 10000Ω. On the other hand, when a positive voltage pulse (voltage 2.4 V, pulse width 100 ns) is applied to the upper electrode, the element A increases from the low resistance state to the high resistance state.

  13 and 14 are diagrams showing resistance change characteristics of the element B and the element C, respectively, when a voltage pulse is applied under the same conditions as in FIG. Comparing FIG. 13 and FIG. 14, between the element B and the element C in which the tantalum oxynitride thin film was formed at the same substrate temperature of 400 ° C., the total ratio of oxygen and nitrogen in the film was high, It can be seen that the resistance change characteristic of the element C having a higher specific resistance value is slightly worse than that of the element B having a lower specific resistance value (the resistance ratio between the high resistance state and the low resistance state is smaller).

  Here, when the lower electrode 205 shown in FIG. 11 is used as a reference, a high voltage is applied to the upper electrode 207, and a positive voltage is applied. When the lower electrode 205 is used as a reference, the upper electrode 207 is lower. When applying a voltage, the negative voltage is applied. As described above, any element can perform resistance change operation at a voltage of 2.4 V or less.

  This is because the voltage pulse applied during the resistance change operation is distributed to both the tantalum oxide layer which is the first resistance change layer and the oxynitrogen deficient tantalum oxynitride layer which is the second resistance change layer. Among them, the component that contributes to the resistance change operation is a component distributed to the tantalum oxide layer through which oxygen enters and exits. By making the resistivity of the tantalum oxide layer higher than the resistivity of the oxynitride-deficient tantalum oxide layer, the voltage component of the voltage pulse distributed to the tantalum oxide layer is increased. It will be possible to operate with voltage.

  In order to confirm this concept, a plurality of three types of planar elements having different manufacturing methods or materials for the second variable resistance layer were prepared, and initial resistance values of 49 elements were measured for each type. Table 1 shows the measured median initial resistance values.

The first variable resistance layer having a high oxygen concentration is Ta ₂ O ₅ having a thickness of 5 nm formed by sputtering, regardless of the type. Further, the second variable resistance layer oxygen concentration is low oxynitride, for each type of thickness 50nm formed by sputtering _TaO x, TaO _x film thickness 50nm formed by CVD, and CVD One of TaO _x N _y having a film thickness of 50 nm formed by the method.

  As can be seen from Table 1, when the second resistance change layer is made of oxynitride, the median initial resistance value is greatly increased. In such a configuration, tantalum oxynitride is a stable compound similar to TaN and has a high barrier property, and metal oxynitride substitutes part of nitrogen atoms in metal nitride with oxygen atoms. Oxygen diffusion from the first resistance change layer to the second resistance change layer is suppressed due to the effect of suppressing substitution sites for the diffusion of oxygen atoms from the interface. As a result, it is presumed that the resistance value of the first variable resistance layer does not decrease.

(Second Embodiment)
FIG. 15 is a cross-sectional view for explaining the configuration of the nonvolatile memory device 30 according to the second embodiment of the present invention. The nonvolatile memory device 30 has the basic configuration of the nonvolatile memory device 10 according to the first embodiment shown in FIG. 1, and includes a resistance change layer embedded in a memory cell hole of an interlayer insulating layer, a first electrode, and a first electrode. It has a configuration in which layers constituting non-ohmic elements are stacked between one wiring. With such a configuration, a sneak current from another element can be limited, and the operation reliability of the nonvolatile memory element is improved.

  The only difference in the manufacturing method from the first embodiment is that the first current control layer 21 is provided between the first electrode 19 and the first wiring 22 in the process described with reference to FIG.

  When the first current control layer 21 is an insulator, the first non-ohmic element 20 is an MIM diode, and when the first current control layer 21 is a semiconductor, the first non-ohmic element 20 is an MSM diode.

When an insulator is used as the material for the first current control layer 21, silicon nitride (Si ₃ N ₄ ) can be used. When a semiconductor is used as the material of the first current control layer 21, a nitrogen-deficient silicon nitride having a nitrogen content lower than that of Si ₃ N ₄ can be used.

  For forming the nitrogen-deficient silicon nitride film, for example, a method of sputtering a polycrystalline silicon target in a mixed gas atmosphere of argon and nitrogen, so-called reactive sputtering method, can be used. As typical film forming conditions, the pressure is 0.08 to 2 Pa, the substrate temperature is 20 to 300 ° C., and the flow rate ratio of nitrogen gas (ratio of the flow rate of nitrogen to the total flow rate of argon and nitrogen) is 0 to 40. %, And the DC power is 100 to 1300 W, and the film formation time can be adjusted so that the thickness of the silicon nitride film is 5 to 20 nm.

  Since the work function of tantalum nitride is 4.6 eV, which is sufficiently higher than the electron affinity of silicon 3.8 eV, when tantalum nitride is used for the first wiring 22, the first current control layer 21, the first wiring 22, A Schottky barrier is formed at the interface. When both the first wiring 22 and the first electrode 19 are made of tantalum nitride, the first non-ohmic element 20 functions as a bidirectional MIM diode or a bidirectional MSM diode.

  In the case of this embodiment, as shown in FIG. 15, the first electrode 19 is completely embedded in the memory cell hole 29 (below the upper opening), and the surface can be processed very smoothly. it can. When the first current control layer 21 is formed on such a smooth surface, a dense and continuous layer can be obtained even when the layer is thin, and the withstand voltage (relatively high) of the first current control layer 21 can be obtained. It is possible to appropriately ensure the characteristic that dielectric breakdown does not occur even when a voltage is applied.

  Since the first electrode 19 is entirely covered with the first current control layer 21, the first current control layer is a concern for the conventional non-ohmic element in which all layers are embedded in the memory cell holes. In the outer peripheral region 21, current leakage caused by the direct contact between the first electrode 19 and the first wiring 22 without the first current control layer 21 does not occur.

  Since the first wiring 22 is provided outside the outer periphery of the first electrode 19 when viewed from the thickness direction of the substrate, the path of the current flowing through the first non-ohmic element 20 is viewed from the thickness direction of the substrate. The first electrode 19 is formed so as to spread outward from the outer periphery.

  In this case, since the electric lines of force due to the electric field spread in the horizontal direction from the first electrode 19 in the memory cell hole 29 toward the first current control layer 21, the first non-ohmic element 20 (MIM The effective area of the diode or the MSM diode) is larger than that of a conventional non-ohmic element in which all layers are embedded in the memory cell hole.

  Therefore, it is possible to obtain the first non-ohmic element 20 made of an MIM diode or an MSM diode having a larger current capacity than that of the prior art and a small variation in characteristics.

(Modification of the second embodiment)
Next, a modification of the nonvolatile memory device having the first non-ohmic element will be described.

  FIG. 16 is a cross-sectional view showing an example of the configuration of the main part of a nonvolatile memory device 31 according to a modification of the second embodiment of the present invention. Each component in FIG. 16 is assigned the same reference numeral as a component having the same function in the nonvolatile memory device 30 in FIG.

  As illustrated in FIG. 16, the nonvolatile memory device 31 is different from the nonvolatile memory device 30 in the shapes of the second resistance change layer 18 b and the first electrode 19, and the first electrode 19 is the memory cell hole 29. It is common to be completely embedded inside.

  The nonvolatile memory device 31 may be formed, for example, according to the following manufacturing method.

  First, in the first embodiment, a process similar to the process described with reference to FIGS. 3 to 5 is performed, so that the process is performed on the third interlayer insulating layer 16 and inside the memory cell hole 29 as shown in FIG. A structure in which the first variable resistance material layer 181a is formed is created. Thereafter, the second variable resistance material layer 181b is formed by a CVD method so as to fill the memory cell hole 29 'in which the first variable resistance material layer 181a is formed.

  Next, before forming the first electrode material layer 191, a portion of the second variable resistance material layer 181 b and the first variable resistance material layer 181 a that covers the surface of the third interlayer insulating layer 16, and the memory cell hole 29 A portion above the upper opening (a portion having a higher height from the substrate than the upper end surface of the third interlayer insulating layer 16) is removed using a CMP process.

  At this time, a part of the upper surface of the second variable resistance material layer 181b is removed to a position lower than the upper end surface of the third interlayer insulating layer 16, and a recess peculiar to the CMP process is formed. A first electrode material layer 191 is formed on the second variable resistance material layer 181b and the third interlayer insulating layer 16 by a CVD method so as to fill the recess. Then, again using the CMP process, the portion of the first electrode material layer 191 covering the surface of the third interlayer insulating layer 16 and the portion above the upper opening of the memory cell hole 29 are removed.

  Thereafter, the non-volatile memory device 31 is completed by executing the steps described in FIG. 9 in the first embodiment.

  Also in the nonvolatile memory device 31, as in the nonvolatile memory device 30, the first electrode 19 is completely embedded in the memory cell hole 29, and the first wiring 22 is the first when viewed from the thickness direction of the substrate. Since it is provided outside the outer periphery of the electrode 19, the first electrode 19 and the first wiring 22 can be directly compared with the conventional non-ohmic element in which all layers are embedded in the memory cell hole. The first non-ohmic element 20 having no larger current area and no concern about current leakage due to contact can be obtained.

(Third embodiment)
FIG. 17 is a cross-sectional view for explaining the configuration of the nonvolatile memory device 40 according to the third embodiment of the present invention. This non-volatile memory device 40 has a basic configuration of the memory cell array of the non-volatile memory device 30 of the second embodiment shown in FIG. 15, and this basic configuration is stacked as a structural unit to form a multilayer memory cell array. is there. By stacking the memory cell arrays in this way, a larger capacity nonvolatile memory device can be realized.

  The nonvolatile memory device 40 exemplifies a configuration in which variable resistance elements and non-ohmic elements are stacked in three stages, but the first, second, and third stage memory cell arrays. In order to make it easy to understand each of the components, the first level is distinguished by adding the first level, the second level by the second level, and the third level by the third level. . In the following, the same components as those included in the nonvolatile memory device 30 are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

  Hereinafter, the configuration of the nonvolatile memory device 40 of the present embodiment will be briefly described. In the case of the nonvolatile memory device 30 shown in FIG. 15, the first wiring 22 extends to the outside of the region where the first variable resistance element 17 and the first non-ohmic element 20 are formed in a matrix. The structure is extended.

  On the other hand, in the nonvolatile memory device 40 of the present embodiment, the second backing wiring 27 and the second electrode wiring 152 which are separate components from the first wiring 22 also extend over the first wiring 22 in the matrix region. Is provided. Such a structure is provided in the second and third stages as well.

  When the first wiring 22 of the first stage and the second backing wiring 27 of the second stage are made of the same material, one common wiring layer is formed between the first stage and the second stage. You may share. Such sharing is also possible in the second and third stages.

  A fifth interlayer insulating layer 47 is further formed on the fourth interlayer insulating layer 23 including the second backing wiring 27 and the second electrode wiring 152. The fifth interlayer insulating layer 47 is provided with a memory cell hole at a position corresponding to the first resistance change element 17, and a third resistance constituting a second-stage resistance change layer in the memory cell hole. The change layer 42a, the fourth resistance change layer 42b, and the second electrode 43 are embedded.

  Then, the second current control layer 45, the second stage second wiring 46, and the third backing are connected to the second electrode 43 and formed in a strip shape in a direction intersecting with the second backing wiring 27 when viewed from the thickness direction of the substrate. A wiring 49 and a third electrode wiring 153 are formed. Further, a sixth interlayer insulating layer 48 is formed so as to bury them.

  A seventh interlayer insulating layer 52 is formed on the third electrode wiring 153 and the sixth interlayer insulating layer 48. The seventh interlayer insulating layer 52 is provided with a memory cell hole at a position corresponding to the first resistance change element 17 (first stage storage unit) and the second resistance change type element 41 (second stage storage part). In the memory cell hole, a fifth resistance change layer 54a and a sixth resistance change layer 54b constituting the third stage resistance change layer, and a third electrode 55 are embedded.

  The third current control layer 57, the third wiring 58, and the third electrode 55 are connected to the third electrode 55 in a band shape in a direction intersecting the third backing wiring 49 and the third electrode wiring 153 when viewed from the thickness direction of the substrate. A fourth backing wiring 59 is formed. Further, an eighth interlayer insulating layer 60 is formed to bury and protect them.

  The second-stage resistance change layer (comprising the third resistance change layer 42a and the fourth resistance change layer 42b), the second electrode wiring 152 in the region sandwiching the second-stage resistance change layer, and the second The electrode 43 constitutes the second variable resistance element 41 (second-stage storage unit). The second electrode 43, the second current control layer 45, and the second wiring 46 constitute a second non-ohmic element 44.

  Further, the third-stage resistance change layer (configured by the fifth resistance change layer 54a and the sixth resistance change layer 54b), the third electrode wiring 153 and the third electrode wirings in the region sandwiching the third-stage resistance change layer The electrode 55 constitutes a third resistance variable element 53 (third stage storage unit). The third electrode 55, the third current control layer 57, and the third wiring 58 constitute a third non-ohmic element 56.

  Further, the first backing wiring 15 is connected to the source region 12 a of the active element 12 through the second embedded conductor 24, the first embedded conductor 25, and the circuit wiring 26. Similarly, the second backing wiring 27 is connected to another active element (not shown) via another buried conductor (not shown) and another circuit wiring (not shown).

  Further, as shown in FIG. 17, the third lining wiring 49 includes a fifth embedded conductor 50, a fourth embedded conductor 51, a first electrode wiring 151, a first lining wiring 15, a second embedded conductor 24, a circuit wiring 26, And connected to the source region 12 a of another active element 12 through the first buried conductor 25. Similarly to the second backing wiring 27, the fourth backing wiring 59 is also connected to different active elements (not shown) via different embedded conductors (not shown) and different circuit wirings (not shown). ing.

  The first backing wiring 15 and the second backing wiring 27 in the first stage are each a bit line or a word line, and are connected to, for example, a bit line decoder and a word line decoder used in a general memory driving circuit, respectively. Is done. Similarly, the second backing wiring 27 and the third backing wiring 49 are each a bit line or a word line, and are connected to the bit line decoder and the word line decoder, respectively.

  However, when the second backing wiring 27 constitutes a bit line in the first stage, the bit line is constituted also in the second stage, and the third backing wiring 49 constitutes a word line. Designed. Further, when the third backing wiring 49 constitutes a word line, the fourth backing wiring 59 is designed to constitute a bit line.

  As described above, in the case of the nonvolatile memory device 40 according to the present embodiment, the first resistance change element 17, the second resistance change element 41, the first resistance change element 17 provided in each stage (each layer of the multilayer memory cell array). Since the first non-ohmic element 20, the second non-ohmic element 44, and the third non-ohmic element 56 are individually provided for the three-resistance variable element 53, they are provided in the respective stages. Writing and reading of the first resistance change element 17, the second resistance change element 41, and the third resistance change element 53 can be performed stably and reliably.

  The manufacturing process of the nonvolatile memory device 40 having such a multi-stage storage unit and a non-ohmic element may be basically repeated by the steps included in the manufacturing method of the nonvolatile memory device 30 of the second embodiment. .

  The nonvolatile memory device according to the third embodiment described above has a memory cell array of the nonvolatile memory device 30 according to the second embodiment shown in FIG. 15 as a basic configuration, and this basic configuration is stacked as a structural unit to provide a multilayer memory. It constitutes a cell array. However, instead of the configuration shown in FIG. 15, the memory cell array of the nonvolatile memory device 31 according to the modification of the second embodiment shown in FIG. 16 is used as a basic configuration, and this basic configuration is stacked as a structural unit. It is also possible to configure a memory cell array. Also with this configuration, the same effect as in the third embodiment can be obtained.

  The nonvolatile memory device of the present invention includes two resistance change layers having different oxygen contents in a hole, and one of the layers has a lower oxygen concentration than the other layers and is a metal oxynitride lacking oxynitrogen. Therefore, the oxygen diffusion between the resistance change layers can be reduced, which is useful in various electronic device fields.

10, 30, 40 Nonvolatile memory (ReRAM)
DESCRIPTION OF SYMBOLS 11 Substrate 12 Active element 12a Source region 12b Drain region 12c Gate insulating film 12d Gate electrode 13 First interlayer insulating layer 14 Second interlayer insulating layer 15 First backing wiring 16 Third interlayer insulating layer 17 First resistance variable element 18a First 1st resistance change layer 18b 2nd resistance change layer 19 1st electrode 20 1st non-ohmic element 21 1st current control layer 22 1st wiring 23 4th interlayer insulation layer 24 2nd embedded conductor 25 1st embedded conductor 26 Circuit wiring 27 Second backing wiring 28 Third buried conductor 29 Memory cell hole 41 Second variable resistance element 42a Third variable resistance layer 42b Fourth variable resistance layer 43 Second electrode 44 Second non-ohmic element 45 Second current control layer 46 Second wiring 47 Fifth interlayer insulating layer 48 Sixth interlayer insulating layer 49 Third backing wiring 50 Fifth buried conductor 51 4th buried conductor 52 7th interlayer insulation layer 53 3rd resistance change element 54a 5th resistance change layer 54b 6th resistance change layer 55 3rd electrode 56 3rd non-ohmic element 57 3rd current control layer 58 3rd Wiring 59 Fourth backing wiring 60 Eighth interlayer insulating layer 151 First electrode wiring 152 Second electrode wiring 153 Third electrode wiring 181a First variable resistance material layer (first deposited film)
181b Second variable resistance material layer (second deposited film)
191 First electrode material layer 200 Substrate 201, 211 Wiring 204, 210 Contact plug 205 Lower electrode 206 Resistance change layer 206a First resistance change layer 206b Second resistance change layer 207 Upper electrode

Claims (6)

A first electrode wiring formed in a strip shape on the substrate;
An interlayer insulating layer formed on the first electrode wiring and the substrate;
A memory cell hole extending through the interlayer insulating layer and reaching the first electrode wiring;
In the memory cell hole, a resistance change layer formed in a region covering the bottom and side surfaces of the memory cell hole;
A first electrode formed in the memory cell hole on the variable resistance layer;
On the first electrode and the interlayer insulating layer, a first wiring formed in a strip shape in a direction intersecting the first electrode wiring at least in a region covering the opening of the memory cell hole;
With
The resistance change layer includes a first resistance change layer made of an oxygen-deficient transition metal oxide and a first oxygen change-deficient transition metal oxynitride having an oxygen content different from that of the first resistance change layer. A laminated structure with two resistance change layers,
When the transition metal is represented by M, the composition of the first variable resistance layer is expressed as MO _z , and the composition of the second variable resistance layer is expressed as MO _x N _y ,
z> (x + y)
A non-volatile storage device that satisfies the relationship   2. The nonvolatile memory device according to claim 1, wherein the first resistance change layer is in contact with a bottom portion and a side surface of the memory cell hole, and the second resistance change layer is in contact with the first resistance change layer.   The nonvolatile memory device according to claim 1, wherein the transition metal is any one transition metal selected from the group consisting of tantalum, hafnium, zirconium, nickel, and titanium.   The nonvolatile memory device according to claim 1, wherein the transition metal is tantalum.   The nonvolatile memory device according to claim 4, wherein the total number of oxygen atoms and nitrogen atoms in the oxynitrogen-deficient tantalum oxynitride is 50 to 70 atm%.   The nonvolatile memory device according to claim 1, wherein a first current control layer is disposed between the first electrode and the first wiring.

Images